This application claims the benefit of German patent application DE P 10062479.0 filed Dec. 14, 2000, herein incorporated by reference.
The present invention relates to a method of winding a traveling yarn at a work station of a yarn winding machine, such as a spinning bobbin winding machine or a bobbin winding machine.
German Patent Publication DE 38 01 964 A1 teaches a method and a device for restoring the spinning operation at an OE (open end) spinning station after an interruption. The spun yarn is wound at the particular spinning station onto a take-up bobbin in the form of a cheese. An autonomous, movable yarn joining or piecing unit is delivered to the spinning station upon a yarn interruption during the bobbin winding operation, that is, between the start of the winding of a yarn end onto an empty tube and the finishing of the cheese, as well as upon a bobbin replacement. In order to eliminate a yarn break, the yarn end is automatically drawn back from the take-up bobbin being formed as a cheese after a first joining program of the joining unit, delivered to the spinning element of the spinning station, placed on the spinning fibers present thereat or fed thereto and is then continuously drawn off from the spinning element as a rejoined yarn, transferred to the spinning station and wound onto the cheese.
German Patent Publication DE 196 40 184 A1 describes a method for cleaning yarn defects or flaws at a winding head of a bobbin winding machine. Yarn defects detected by a sensor are completely cleaned with this method whether they are long or short yarn defects. To this end, the length of the yarn with a defect is determined after the occurrence of a yarn defect between the time of the occurrence of the defect and the time of the yarn cut. A suction tube is positioned in front of the take-up bobbin in order to remove the yarn pieces with defects. The yarn end is unwound, the entrance of the yarn determined by a sensor located in the suction tube and the yarn length unwound from the take-up bobbin and traveling into the suction tube determined. The unwinding process is stopped when a sufficient yarn length has been drawn into the suction tube on the basis of the determined yarn length that, during the subsequent placing of the yarn drawn from the take-up bobbin into the yarn-end joining device, the yarn length which was wound onto the take-up bobbin subsequent to the occurrence of the yarn defect remains outside of the yarn-end joining device for separation.
Yarn joining locations that can be present in the form of knots, splices or other forms of yarn end joinders are practically unavoidable after yarn interruptions during the winding process and during the bobbin winding operation. It is disadvantageous for economic reasons to unwind the entire yarn previously wound onto the tube after a cleaning step and to draw it off as waste in order not to have to accept any yarn joining locations in the yarn. The production of relatively large-volume cheeses from several spinning cops is not possible at all without yarn joining locations. Since a yarn joining location must necessarily be generated to join the yarn end drawn off from the already wound yarn of the bobbin being formed into a cheese to the yarn source, e.g., a spinning station or element, the yarn joining locations are tolerated in the finished yarn on account of this unavoidable state of affairs even though they constitute imperfections. The imperfection can consist on the one hand in a deviation in thickness of the yarn caused by the yarn joining location. A check for joined-yarn locations is customary in spinning bobbin winding machines during which the thickness of the joined yarn and thick or thin areas in the yarn directly in front of or behind the joined yarn are detected. Such joined yarns that do not meet a given quality criteria can be immediately eliminated with the joined-yarn check and subsequently replaced by a yam joinder that meets these quality criteria. On the other hand, imperfections of color can also occur. For example, a change of the color absorption behavior can occur in a splicing station during the splicing of yarns containing synthetic fibers due to hot air. This change of color absorption behavior can make itself noticeable in a disadvantageous manner during the dyeing process.
In general, a sporadic occurrence of yarn joining locations in a finished textile product, e.g., a fabric, is not important. However, it can occur that two or more yarn joining locations follow each other relatively closely in the yarn. A defect that can hardly be recognized with the naked eye but is nevertheless undesirable or even has the effect of reducing the value can be present due to repeated occurrences in the finished textile product. Such defects can not be excluded when using the known methods and must therefore be accepted.
It is accordingly an object of the present invention to provide an improved method of winding a traveling yarn at a work station of a yarn winding machine, such as a spinning bobbin winding machine or of a bobbin winding machine, which will improve the quality of the winding of a take-up bobbin.
Briefly summarized, the present invention reliably avoids an undesirable accumulation of yarn joining locations that form a recognizable defect in the finished product by determining, upon the occurrence of a yarn interruption, the amount of yarn wound since the last yarn joinder and, if this amount of yarn is less than a predetermined amount, such an amount of yam is unwound from the take-up bobbin and the unwound yarn end is removed such that the preceding yarn joining location is in the removed yarn section.
Whether or not the predetermined yarn amount has been met can be determined in an especially rapid and simple manner if the time elapsed since the restart of the winding process after the last yarn joinder is determined as a measure for the wound amount of yarn and a time span is set as the predetermined criterion. The yarn length corresponding to the amount of yarn wound onto the take-up bobbin is determined, this yarn length is unwound off the take-up bobbin and the unwound yarn end is separated and removed. By also removing a predetermined yarn length in addition to the determined yarn length, it is assured that the previous yarn joining location is in the separated yarn section. The removal of the separated yarn end can take place in a customary manner by suction removal.
As an advantageous alternative, the yarn length wound onto the take-up bobbin since the preceding restart of the winding process after the last yarn joinder is immediately determined as a measure for the wound amount of yarn and a length is set as the predetermined amount. If the predetermined yarn length set as the criterion is not achieved, the determined length of wound yarn can be used immediately without further recalculation as the length that is to be unwound again.
The method of the invention can be used advantageously in spinning bobbin winding machines in which the spinning unit or the spin box is the yarn source and in winding machines in which a feeding bobbin functions as yarn source.
It is possible with the method of the invention to achieve an effective improvement of quality in a simple manner in the finished yarn as well as also in particular in the finished textile product in which the yarn has been processed.
Further details, features and advantages of the invention will be explained in and understood from the following description with reference to the accompanying drawings.